In the formation of semiconductor devices, there may be a need to incorporate small amounts of some other material, which will be called a dopant, into a solid layer or feature. Semiconductor materials, most commonly silicon, are routinely doped with p-type or n-type dopants to enhance conductivity.
Shallow doping is often achieved by ion implantation, in which dopant ions are accelerated into a layer of a semiconductor such as silicon. For example, boron or phosphorus ions may be implanted into silicon to dope it. Since the ions are implanted at a given implantation energy, this method is best adapted to dope a planar region of a planar surface.
In some devices, however, it may be may be necessary to dope a surface which is not planar, forming a non-planar doped region. It would be advantageous to dope a non-planar surface in an isotropic or nearly-isotropic manner.